Cummins/Onan MDJA Generator Set

⚠ Do not force needles against seats.

1. Open both needles 1 to 1-1/2 turns off seats.
2. Apply full load; turn main fuel screw in until speed drops, then out to normal.
3. Remove load; turn idle screw out until speed drops, then in to normal.

1. Loosen locknuts on governor linkage, remove link at one ball joint.
2. Position governor arm and fuel control arm fully forward.
3. Adjust linkage so both ball joints fit without moving arms.
4. Tighten locknuts.
5. Release fuel solenoid plunger.

Tools: feeler gauge, socket wrench

1. Turn flywheel to compression stroke for cylinder to adjust.
2. Turn flywheel clockwise additional 10 to 45 degrees.
3. Loosen locknut to increase clearance, tighten to reduce.
4. Use feeler gauge to set proper gap.
5. Adjust in firing order 1-2-4-3.

Tools: feeler gauge, wrench

1. Remove valve covers.
2. Crank engine until intake valve opens and closes.
3. Continue 1/4 turn until timing marks align.
4. Turn adjusting screw to obtain correct clearance.
5. Use flat feeler gauge between valve and valve rotator.

⚠ Avoid overcharging.

Tools: DC ammeter

1. Set slide tap on resistor R4 to about 2 amperes charging rate.
2. For frequent starts, increase charge rate slightly until battery stays charged.
3. Stop engine when readjusting to avoid shorts.

⚠ If the screw is tightened more than 1 turn, the exhaust valve could hit the piston.

Tools: Feeler gauge

1. Set valves to correct clearance and leave flywheel at 10° ATC.
2. Set the arm in the decompression position.
3. Turn the set screw so the end just touches the exhaust rocker arm.
4. Turn the screw exactly 1 revolution clockwise.
5. Hold the set screw and tighten the lock nut hand tight, then 1/4 to 1/2 turn farther.
6. Release the mechanism and check clearance between screw and rocker arm.

1. Install pump with 0.006-inch (0.15 mm) shims.
2. Loosen delivery valve holder to relieve spring pressure.
3. Rotate flywheel to about 15 degrees before port closing point.
4. Blow in pump inlet and rotate flywheel slowly clockwise until air stops.
5. Measure distance from port closing point to PC mark.
6. Select shims from table and install pump.

⚠ A too close sensitivity adjustment approaching no speed drop can cause hunting.

1. Adjust for minimum speed drop without a hunting condition.
2. If speed drops too much at full load, unscrew the governor adjusting stud to use more coils of the spring.
3. Hold the stud and turn the speed nut slightly for more spring tension to compensate for reduced rpm.

Tools: Tachometer

1. Hold the governor spring stud and turn the nut clockwise to increase rpm.
2. Turn the nut counterclockwise to reduce governed speed.
3. Hold a tachometer against the stud in the axis of the generator.

1. Remove flywheel and examine breaker points.
2. Adjust gap to .022 inch (0.56 mm) at full separation.
3. Loosen screw to shift point set, retighten securely.

1. Set the maximum stop screw while gradually increasing load to stop the throttle at smoke point.
2. Set the minimum stop screw to just fully close the throttle with no fuel injected.

Tools: continuity light, thickness gauge

1. Crank engine to fully open breaker points.
2. Loosen locking screws and turn cam to adjust.
3. Set point gap to .020 inch (0.51 mm).
4. Shift breaker point box to align timing mark.